Abstract :
Polycrystalline sample of Tb3Cu4Si4 compound was prepared and studied by magnetic and powder neutron diffraction measurements. Tb3Cu4Si4 crystallizes in the orthorhombic Gd3Cu4Ge4-type structure (space group Immm). In this structure the Tb atoms occupy two non-equivalent crystallographic positions: 2d and 4e. Below TN equal to 50 K the Tb moment in the 2d site orders and forms a collinear magnetic structure. At the temperature of Tt1=38 K a transition from the commensurate magnetic structure, described by the propagation vector k2=(0,12,0) to an incommensurate one, described by the propagation vector k1=(0,0.515,0), is observed. Below Tt2 equal to 7 K the Tb moment in the 4e site forms a sine-wave modulated structure described by the propagation vector k3=(0.23,12,12).
